Energy transfer during resonant neutralization of hyperthermal protons at an aluminum surface studied with time-dependent density functional theory

Abstract

We present time-dependent density functional molecular dynamics (TDDFT-MD) simulations with an adiabatic approximation to the exchange-correlation potential for hyperthermal protons (${\mathrm{H}}^{+}$) with initial kinetic energies in the range of 2--50 eV impinging on the fcc-hollow site and the on-top site of an Al(111) surface. The surface is modeled by a finite-size cluster and the results are generalized to ${\mathrm{H}}^{+}$-Al surface scattering. From the simulation, neutralization distances are determined and the time development of the kinetic energy and the electronic excitation energy are derived. The results can be rationalized on the basis of the ground-state potential energy surface and the ${\mathrm{H}}^{+}$-Al(111) interaction potential. Furthermore, the difference in initial kinetic energy between ${\mathrm{H}}^{+}$ and ${\mathrm{H}}^{0}$ projectiles required to yield identical exit velocities is derived. Notably, this difference changes sign within the studied range of kinetic energies. This is traced back to the neutralization distances and the difference between both the ground-state potential energy surface and the ${\mathrm{H}}^{+}$-Al(111) interaction potential at those distances.